1. Field of the Invention
The present invention relates to a reflection plate for semiconductor heat treatment and more particularly to a plate for a heater to be used for semiconductor heat treatment, a reflection plate to be used for a semiconductor heat treatment reactor, or a reflection plate to be placed on a wafer board for heat treating semiconductors such as dummy wafers.
2. Description of the Related Art
In the field of semiconductor manufacturing, reflection plates of various shapes and sizes are used for reflecting heat radiating from a heating element. More specifically, reflection plates of heaters for semiconductor heat treatment, reflection plates to be used for a semiconductor heat treatment reactor, or dummy wafers to be plate on a board may be exemplified.
Such reflection plates must meet requirements such as absence of dust, corpuscles, or particles which might be resulted therefrom; sufficient corrosion resistance because ambient gases are highly corrosive in many cases.
As a solution to satisfy the above requirements, the applicant proposed a reflection plate of the heater to be used in the semiconductor heat treatment in Japanese Patent Application Laid Open to the Public No. 2000-21890, referring to which an explanation will be given as follows with reference to FIGS. 8 and 9.
In FIG. 8, a reflection plate 20 is composed of a plate-like quartz glass support member 21 and a reflection plate 22 of carbon having at least one mirror side, said reflection plate 22 being sealed in the plate-like quartz support member 21.
Said reflection plate 20 has been assembled by putting together a quartz glass upper plate portion 21a, said reflection plate 22 having at least one mirror side, and a quartz glass lower plate portion 21b having a countersunk seat 21c (recess) for the reflection plate, all of said elements being subjected to fusion treatment after the assembly work as shown in FIG. 9 such that said quartz glass upper plate portion 21a and said quartz glass lower portion 21b of the quartz glass support member are made integral.
With said reflection plate 20, the carbonaceous reflection plate 22 covered in said quartz glass support member 21 provides protection against the production of dust, corpuscles, particles, or the like as well as providing sufficient corrosion resistance.
It is to be noted here that said reflection plate for semiconductor heat treatment are used in the reactor environment under a temperature of 200 to 1200° C.
For this reason, a technical problem still remains that said carbonaceous reflection plate reacts with the ambient gas within the interior space defined by the countersunk seat 21c (recess) for the reflection plate or with the quartz glass to result in foreign material adsorption as a result of such reaction therewithin.
Furthermore, the reaction gas produced by the carbonaceous reflection plate or the quartz glass cause a rise of local gas pressure between the carbonaceous reflection plate and the quartz glass body in contact therewith with the result that said quartz glass body tends to crack or deform.
Furthermore, it is to be noted that said quartz glass reflection plate 22 is accommodated in said quartz glass lower portion 21b having a countersunk seat 21c (recess) before the quartz glass upper portion 21a is placed thereon so as to cover the countersunk seat 21c (recess), the weight of said quartz glass upper portion 21a being applied thereonto at a temperature of as high as 1,200° C. or more to be subjected to the fusion treatment.
At this time, there is a likelihood that the interspatial gas produced by moisture adsorbed on the carbonaceous reflection plate, residual gas or a gas in the space defined by the countersunk seat 21c (recess) for the reflection plate can expand while the quartz glass body defining the sealed space can expand, deform or fracture.